Telephone kepeatee



y sept. 4, 1923.` 1,466,858

s. sUEKoEF TELEPHONE REPEATER l Filed May 16. 1919 sheets-s eet 1 5m27.117s] UEZm/f EEZ-'275 F1' .ZPTZTE septg4, 1923. 1,466,858

s. sUEKQFF I TELEPHONE REPEATER File 'cs-Sheet 2 E; 7 Zfbrney 552222152 UEAUJ Sept. 4, 1923. u

l S. SUEKOFF TELEPHONE REPEATER 4 sheets-snet Filed May 16, 1919 wel? UP; 552771257 UEUf/f s. sUEKol-'F TELEPHONE REPEATER Sept, 4, 1923.

Filed May 16. 1919 4 Sheets-Sheet 4 NIJ/51W' 55727125] EUEUf/ Patented Sept. 4, 1923.

UNIT so sTATES 1,466,858 PATENT OFFICE.

SAMUEL sonneri", or onroiieo, 1LL1no1s,1AssrGNon 'ro KnLnoGG SWITCHBOABD AND surrLY COMPANY, or CHICAGO, inriiriois, ii Conronnrren ci? Immers.

TELEPHONE nnrniirnn.

rimplication filed May 16, i919. Serial No. 297,468.

To all whom itmag/ Concern:

Be it known that I', SAMUEL Sunirorr, a citizen of the United States oit` America, residing at Chicago, in the county otCoolr and Stater ot Illinois, `have invented certain 'new )and useful Improvements in Telephone Repeaters, of which the following is a specification.

lily/f' invention relates to. transmission systems andhas moreparticularly to do with speech transmission*over toll Vor long distance telephone` lines. One of the objects of the. invention is to increase theftransmission eiiciency by means of a simpliiied repeater circuitv arrangement, which may be constructed cheaply yet yoperate vetliciently and require very little maintenance. long distance transmission circuits, the transmission losses are rated in cable miles,

notion of the lines overwhichtlie Vconnection is set up,and are etten very serious, f` An object ot my invention ,ist the provision oi a telephone.repeater inrwhicli these trans V mission losses laresubstantially.eliminated.

illustrates rdiagrammatically a toll or long distance connection operatingin association with the repeaterr ot my invention;

Fig. 2 is a. plan View of the voice current relay of my invention;

Fig. l isa trent elevation of the relay;

Fig. i is a right side view of 2;

Fig.` 5 is a vievvy of one oi the vibrato-ry members, and'y i 1 'Y Fig. 6 is a perspective view of the vibratory tongue. f f

Referring to Fig. 1.,'part l, I illustrate calling local battery ksubstation A con neffting at the exchange' with the usual drop signal DS and jacl; il. The magnetoy cord mprises answering plug All?, lug'CP and the usual clearing and vary according to the nature and con-y from ringing generator G Vout drops CD and CD' bridged across the cord conductors; also a listening key LK and a ringing key RK. A trunk jack TJ vis shown and its'a-ssociated drop signal DS' is actuated when a distant exchange vWishes connection with a subscriber at the exchange in Which the trunk jack TJ is located. This apparatus is associated with the repeater circuit RE of my invention, as illustrated n Fig. l, part 2.

The repeater circuit RE in Fig. l, part 2 comprises an operating relay- OP, which actuates When a plug is insertedin the trunk jack TJ With Wliic-hthe repeater circuit RE is ass ciated. A chain oi"A relays E, F, H and K is provided, which relays function When relay @P actuates to bring about certain necessary circuit changes in the circuit RE, and a voice lcurrent relay'VR is alsofprovided, which is included in the chain relay circuit for purposes as Will be more fully liereinafterdescribed. A repeating coil RC comprises windings 2, 3 and 4, the said windings 2 and i having resistances 5 and 6 in series With them;r amplifier AM comprises an agitating member 7 and an amplifying member 8, and associated lwith it 'are the impedance Vcoils 9 and '10.7 To

vthe right of the repeating coil RC is also a chain of relays E', F', H', and K', which function inalike `manner as relays E, F, H- and K, and a voice current relay VR' isalso provided in association with relays E', F', H', and K', for purposes as Will be more fully hereinafter described. To the right of the drawing, I Yshow a ringing key RK' which connects ringing current from' the ringing generator G' to throw the drop signal BSZ at the distant exchange, vvliich signal is shown with :its associated trunk jack TJ' .in Fig. l, part 3. -The cord circuit C' of Fig. l. part 3 comprises an answering plug AP' and a calling-plug CP', clearing out drop signals CD2 and DS, a

listening lrey LK', Which when actuated connects tlie operators set O' to the Cord conductors, and a ringing key RK2, vvliich when actuated connects ringing current To the right of the drawing, l sliovv a called substation D comprising the usual local battery sub station apparatus, the station terminating at the exchange in a line circuit L' comprising "be usual drop signal S and. its assojack il'. i

Having described in general the apparatus illustratedL in Fig. 1,1 Will now'describe in detail the operation of the apparatus used in establishing a connection, including the operation of the repeater circuit of my invention. i'lssuming that substation initiates a call, the drop signal DS at the exchange falls and the operator inserts the answering plug AP of the cord circuit C into the jack il, opening the jacl; spring contacts and disconnecting` the drop signal DS. tromV the line. She now actuates her listening key LK to connect her opcrators set O to the cord conductors, and inquires the Want of the calling' subscriber,

Assuming` that it is the subscriber D at t-he distant exchange that is Wanted, the operator non inserts the callingplug- Cl) into the trunk jack TJ, leading to the distant exchange and actuates her ringing ley RK', Connecting generator G', which current actuates the drop signal DS2 z t the. distant exchange (Fig. l, part 'lhe operator at the distant exchange noting); the actuated drop signal DB2 inserts the answering plug All' ot the cord circuit C into the trunk jack TJ" associated with the drop signal D82, opening the. jack spring` contacts and disconnecting` the signal D552. She now receives the number olV the called substation from the operator at the originating ein citings. and as We have assumed that it is substation l) that is Wanted, the operator in serts the calling plug` CP' into the jack J' ot that line and actuates the ringing key lll@ to connect eciieratorflg to ring the call bell at substation D. 'lhe subscriber in response to his call signal, removes his receiver from its switch hook and the subscriber at the callingV substation A and the called substation D are now connected and enabled to carry on conycrsation.

l will now describe in detail the operation olf the repeater circuit, as illustrated in Fig. l, part 2. Upon the insertion ot the callingl plugT CP of the cord circuit C into the trunk jack TJ, au energizing circuit torthe operating' relay @E ot the repeater circuit RE is established, traced from battery, through the Winding` ot the operating relay OP, conductor l5. sleeve contact 16 of the jack TJ to ground A17. The operated relay Ol) closes its alternate contact 18, closing an energizing' circuit for the relay F, traced from battery, through the Winding o'f the said relay F, conductor 19. its normal contact 20, conductors 2l and 22, normal contact 23 ot relay K, conductor 2l, closed contacts 25 and 26 ot voice current relay VR, and conductor 2T to @ground at alternate Contact 18 ot relay OP. The relay F ot repeater circuit is also energized by current, traced from battery, through the Winding' ot relay ll', condoctor 19'. normal contact 20' ot relay F', conductors 2l' and 22', normal contact Lacasse ol' relay l', conductor 2l', closed contacts 25' and 26' ol `cioe current relay VR', conductors 2T' and 27 to ground at alternate contact 1S of relay OP. The relay F upon energization opens its normal contact 20, which removes the shunt Yabout relay E and a series energiaing` circuit for relays E and F established, traced from battery, through the Winding; ot rel-ay F, conductors 19 and 28, through the Winding,r of relay E, conductor 22, normal contact 23 ot relay l, conductor 24;, closed contacts 25 and oi relay V conductor 27 to ground at alternate contact 18 ot relay Ol). The closing or alternate contact 29 oi" relay E closes an ene"- gizing circuit for relay H, traced trom battery, through the windimg` o'l' relay H, onduclor 30 to ground at alternate contact of relay The relay F' upon energization opens its normal contact 20 which remotes the shunt about the Winding ol relay E' and a series energizing circuit. is established Y'or relays l' and F', traced from battery, through the winding ot the relay ll', conductors 19' and 28', through the Windingor' the relay E', conductor 22', normal contact oi'f relay conductor 24', closecv contacts and 2G' of relay VR', conductors 2' and 27 to ground at alternate contact 1S ot relay QP. rllhe closin"T of alternate contact 29 ot relay E' closes an energizing circuit tor relay ll', traced trom battery, through the Winding of relay El', conductor to ground at alternate contact 29' ot' reA lay E'. The closing` ot alternate contacts and 33 ot 'relay l connects the agitating meniber i" oi" the amplifier AM, with the tall;- ing conductors and 35, traced from point 36 in conductor 342, over conductor 37,'alternate contact 32 ot relay Gl), conductor 38, through the z gritatingj member 'l ot' 4the ainplii'ier AM, conductor 39, alternate contact 33 o relay Gl), conductor l0 to the point 4l in conductor 35. rl`heclosing ot' contact 42 ot relay Ol connects battery to the ampliler member 8, traced from ground at alternate contact L l2 oli` relay OP, coi'iductor a3. through impedance coil l0, conductor afl, Windina` Y3 ot repeating' coil C, through the amplityincf'member S of theamplier Alti; through the Winding ot' the impedance coil 9 to battery and ground. IUflic amplilier circuit is thus prepared for amplifying" pur poses and the impedance coils 9 and l0 in the above-traced circuit are for excluding battery noise and tor clarifying the amplified voice transmission currents, as is Well understood. rlhe condenser CO is normally bridged across the amplifier circuit, but nhen relays E and E' kare energized, the condenser bridge is disconnected to again be placed in circuit When either party talks, as will be more fully hereinafter described. 'the above circuit operations all take nlace when the relay ill) is energized, as already to the'substation A. The construction ot thel described. rlhe portion ot the circuit to the .lett oi` Jihe repeating coil it@ and the portion to the right of the repeating coil RC are identical, and both operate inthe same manner. y f f llow assuming that the subscriber atthe substation Ais the iirst to -tallnthe tirst voice currents that are transmitted pass i'rom the said substation A through the cord connection, over `conductor 45, alternate contact 46 o t relay E, conductors 47 and48, through the windings otthe voice current relay VR, conductor 49, alternate contact 50 of relay E', conductor 51, alternate contact 52 'of relay E to conductor 53 and back mentarily closed, closing a circuit forv relay K *from battery`v through alternate Contact 54, conductor `55ste groundat now normal contact 56 ot E. vr'Relay Kisthus momen-r tarily energized, opening its normal'` contact 23, thus also opening the circuit ot relay E. As relay VR picks up, due to Voice currents passing through it, its contacts 25 and 26 may possibly vibrate rfor a fraction of av secn ondv before breaking permanently, and relay E might also vibrate infconsequence except that relay K in opening its circuit at/contact 23 allows relay E'to restore'with positiveness, and as relay E restores, relay F'restores. as does also relay H and the momentarilyy energizedQrelay K. The chain oit relays E, F, H. and K are now at normal, but relays E', F and H remain energized at this time." The voice currents ai'ter relay E restores now pass overicon'ductor 45, normal Contact 57, conductor 34 to the point36 thence ovcrconductor 37, alternate contact 32, conductor 38, throughythe agitating member 7, conductor 39, ralternate Contact 33, conductor 4() tothe point. 41 and from thence overconductor `35, normal contact 58 to conductor 53. "The, current passing through the agitating member 7, the latter' actuates theamplifier member 8 by `Which it is repeated into the coil 3 and thence into coil 4 of the repeating coil RC.` ThD circuit throughcoi'l 3 includes condenser CO and the middle switch contact ot relay E. The amplified voice currents now travel from the point 60, over conductor 61, normal contact 80, conductor62, alternate contact 52 ofrelavE; conductor 64,- normal contact of the key RK yand vconductor 66 through the connected substation and back over conductorv 67. normal Contact 68 otkey RK', conductor 69, alternate Contact 46', conducance coil 5 to the other terminal ot the Winding 2.y rThe resistance 5 in series relation, With winding 2 regulates the voice current how through the relay VR and permits only enough current to pass ythrough the said relay tokeep it operated and hold contacts 25 and 26 open to prevent relays E F and H operating While voice currents are traveling toward the ycalled substation D. The resistance 6 is in series relation with the Winding 4 of the repeating coil RC, but when relay E restores, due to the opening of contacts 25 and 26 of relay VR, the resistance 6 is shunted outQthe said shunt extending from the point 60, over conductor 6l, normal contact 8O of relay E, conductor 62 to the point 75 and the amplified voicecurrents in Winding 4 pass out over the talking` conductors to the called substation D With 'full ampliiied Value. The` talking circuit through the repeater circuit RE when' Voice currents are passing from A to D is as follows: over conductor 45, normal contact 57, conductor 34 to the Apoint 36 and thence over cond-uctor 37, Yalternate contact 32 of relay Ol?, conductor 38, through the agitating member 7 of the amplifier AM, over conductor 39, alternate Contact: 33 voi relay QP, conductor 40 tothe point 4l` and thence over conductor 35, normal contact 58l and to conductor 53. The amplified Voice currents are now induced in the Winding 4 ot tlie'repeating coil RC andfiow over conductor 6l, normal contact 8 0, conductor 62, alternate contact 58 oi' relay E', which remains energized when subyscriber Aat substation Ais talking, conductor 64, normal contact 65 or key El@ to conductor 66, to the substation D, back over con` duct-or 67,'normal Contact 68 ofkey RK', conductor 69, alternate'contact 46,', conductor 47 to the upper terminal of the Winding 4 of repeating coil RC. .When the subscriber at substation A stops talking, as at the end of a sentencaY Voice currents stop passing through the voicev current relay VRand contacts 25 and 26` again close, establishing an energizing kcircuit tor relay F, which in turn allows relay E to operate in series 4With it, the relay E in turn closing a circuit for relay-,l-Las previously described, the relay OP, of course, remaining energized until disconnection takes'place.

Assuming now that after 'the subscriber.

at the substation A has reached the end of a sentence, the subscriber at the substation D :begins conversation, the tirst iiow ot voice currents will pass through the voice current relay VR from conductor G7, normal contact 68, conductor 69, alternate Contact 46 of relay E', `conductors 47 and 118', windings ot 4relay VR', conductor 76, alternate contact 50 of relay E, `conductor 612, alter-- nate contact 52', conductor -6-1, normal contact 65 of key RK and conductor 6G. The relay VR operates, due tothe voice currents passing through its windings, and its contacts 25 and 26 are opened to bring about the de-energization of relay E in a manner similar to that previously described in connection with relays E, F, H and l. Upon the (le-energization ot relay E. voice currents now ypass Athrough normal contact 5T oft relay E', conductor Se to the point 36, thence over conductor 37, alternate contact 3Q, conductor 38, agitati-ng member 7, conductor 39, Valternate contact conductor 40 to the point /l-l, over conductor 85,-nor1nal contact 58 to conductor Git. The current thus amplified by member 8 is induced -from winding 3 into the winding 2 oiC the repeating coil RC and this amplilied current passes from the upper te `mina-l ot the winding 2 of 'the repeating coil RG, conductor 4:7, alternate contact 46, conductor 4:5 and through `the calling substation A back over conductor 53, `alternate contact 52, conductor 5l, normal contact 80, conductor 6l to the 'lower terminal of the winding 2 of the l repeating coil RC. The resistance 5 is shunted by the closing ot normal contact of relay E', Jfor purposes similar 'to those already described in connection with resistance 6. A portion of the voice currents is also induced into the winding fi ot repeating coil RC t'rom the upper terminal of winding 4t. conductors 47 and 48, through the windings oit relay VR', over conductor 76, alternate contact 50 of relay E, conductor 62, through resistance 6 to the other terminal of the winding et for the purpose ot keeping relay VR operated to keep the circuits of relays E, F', lil open for purposes already described.

During a lull in the conversation in 'which neither party is talking, a relay VR ot VR restores, depending upon which party talked last. to allow its associated chain of relays E, F, and H or E, F, and H to again energize and the repeater circuit RE remains thus until either subscriber starts conversation, when one or the other of the twin elements will operate as described, depending upon which subscriber' again starts conversation.

From the above description, it may be seen that I have provided a two-way amplifying repeater with twin repeater elements which operate so that when a calling subscriber is talking after a connection has been established, the portion to the left et the repeating coil BC restores, and the portion to the right remains actuated to permit ampliied voice currents to pass out to the called subscriber. Now,y when the called subscriber talks, the port-ion to the right oiE the coil RC restores and the portion to the lett ot the coil remains actuated to permit amplified voice currents to pass out to the calling subscriber. A see-saw action ot the two like elements is brought about as the two subscribers alternately talk. i

ritter conversation has terminated, the subscribers at and D replace their receivers and actuatc their hand generators, throwing the clearing out drops CD and CD3 at their respective exchanges vand the operators at the respective exchanges noting the signal, know that conversation has terminated and withdraw the plugs. rllhe removal oit the plugv CP trom the trunk jack TJ allows relay OP associated with the repeater circuit lilrto restore, and relay Ol) restoring allows relays E, F and il and E', F and H to restore, placing circuit RE at normal. lThe apparatus used in establishing the connection is Anow at normal and available tor establishing other connections.

Assuming now that subscriber at the substation D is the calling subscriber, he actuates his hand generator to throw the drop signal DS3, and the operator inserts the answering plug AP into the jack fl and actua es her listening key LK. Assuming that substation A at the distant exchange is wanted, she inserts the calling plug CP into the trunk jack TJ leading to thi-:exchange into which the subscriber at the called substation terminates and actuates her ringing key lll@ which connects ringing generator current for generator G2, the said current passing` through the drop signal S at the distant exchange, as shown in l, part 'l The operator ot the exchange with which subscriber A is associated inserts the answering plug .AP ot the cord C into the truuk jack TJ Aand receives the number ot the subscriber wanted, which we assumed is the subscriber at substation A. The insertion ot the calling plug CP into the jack J and the actuation ot the ringing key RK connects the ringing generator G to ring the call bell of the subscriber at substation A.

The insertion oi the answeringV plug J3 into the ack TJ closes an energizing lcircuit for the opera-ting relay OP of the repeater circuit- RE and the operating relay OP actuating causes the operation or the relays E, ll and l-l and E', ll and H. as already described. Now, when the subscriber at the called substation A. answers, the subscribers and D are in conversa-tional circuit and the repeater circuit will operate in the same manner as previously describe-d, as is also the restoration to normal of the apparatus used in establishing the connection i forces the members 114 and 115k apart.`

Referring nowL toFigs. 2 to G inclusive, I illustrate `in detail the voice current relay VR, as described in connectionfwitli Fig.l y1. They relayas showncomprises a lol-shaped magnet 100 suitably supported on a base 101 by means ota yolreniember 102, which is secured tov the said base 101 by means of screws 103.` Magnet coils`104 and 105 are provided and are mounted upon the legs 106 and 107 ot the U-shapedinagnet 100. A vibrant tongue 1080i thin ieXible material is Vsecured at its one end to al bracket 109 by means'ot the screws 110, the said bracket 109 in turn being secured to the base 101 by means of screws 111; The tongue 108 has a flexible portion 108 and a rigid portion 41082 formed by means of the angular ertensions 1083, 'for purposes as will be presently described. rlhe tongue 108 rests at an intermediate point against a stop 112 which is secured rto the base 101 by means of screws 113, and the relation of the stop 112 and tongue v108 will be presently described. A pair oit pivotally suspended vibratory ,membersV 114 and 115 is provided, which are pivotally secured by means of the pivot pins 116 and 117. The pivot pins 116 and 117 are secured to the bracket 118 in any suitable manner, the said bracket 118 beingsecuredto the base 101 by means ofthe screws 119. The members 114 and 115 are similar in construction and a description rot the. member 114 is sufficient. The member 114 is constructed of a piece ot glass tubing 120 haw ing an enlarged globular" end 121 to which a contact 122 is suitably secured,`the said contact 122 being connected lwith the terminal 123 bymeans ofthe wire connection 124 ywhich passes through the central opening ofthe member 114. The member 114 is also provided with a hooked or looped end 125by which the said member is supported on its pivot pin 116.

The tree end ot the tongue 108 is provided with a pair of contacts 126 and 127, which are normally in engagement with the contacts 122 and 128 on the respective vibratory members 114and 115.

The relay VR is ail'ected by voice currents and operates through the different ranges ot frequencies of kvoice currents, they range being 216 for the lowest and 1500 Afor'y the highest. The natural rate of vibration oi the members 114 and 115 is below the lowest rate of the voice currents and when voice currents pass through the coils' 104 and 105, the tongue is set into vibration, and this vibration or the tongue 108 being permitted, due toits flexible portionlOS. The end 1084 of the tongue 108 is also set into vibration, due to the stop 112 being in engagement with the tongue and y.this vibraticin L S thenatural rate of vibrationof the members I 114 and 115 is lower than the lowest-rate of the voice currents, the said members are kept apart, due tothe vibration of the end 108AL of the tongue keepingtlie contacts 126, 122, 12'? and 128 open as long as voice curientsvare passing through the magnet coils 104 and 105 for purposes 'already described in connection with Fig. 1.

The lines A and D may be toll lines insteadof subscribers lines. By constructing the relays in a desired manner, I find that they maybe made toworlr with greatdis- Vpatch and accuracy, therebycausing a very etlicientl operation of the circuit arrangement.

While have illustrated my 'invention operating in connection with a specic circuit arrangement, I do not wish `to be limited `to the saine as the circuit of my invention 'is applicable with other circuit arrangements, and I also do not wish to bey limited to the exact arrangement as shown, as many Y changes and modifications are readily-apparent, and I, therefore, aim to cover all such 'changes and modifications as come within the spirit and scope ot the appended claims. Having described my invention, what I claim asnew and desire to secure by United ently of said primary energizing circuit during transmssion of voice currents from said calling telephone.` f

2. A system of the character described including a calling telephone and a called telephone, aA circuit for connecting said telephones, a pair ot voice' current relays, and a repeater 'tori said circuit, nieansincluding a. chain ot relays controlled by o-ne or' said voice current relays for connecting said repeater so that the voice currents transmitted trom the calling telephone are amplified and retransmitted Ato the called telephone,

vmeans including a chain ot relays controlled by said other voice current relay for cony necting said repeater so that the voice currents transmitted from the called telephone Vare amplified and retransmitted to the calltelephone, a primary energizing circuit for said one relay including said 'calling tele phone line, another circuit,l for maintaining said one` relay 'energized independently of said primary energizing circuit when voice currents are being amplified and retransmitted to the called telephone, a primary energizing' circuit for said other relay including said called telephone, and another circuit for maintaining said other relay energized independently ot said second primary energizing' circuit when voice currents are being retransmitted to the calling' telephone.

` A system of the character described including a calling microphone and a called telephone, a circuit for connecting' said microphone and said telephone including' a voice current relay normally disconnected from said circuit and a telephone repeater, said voice current relay vwhen connected in said circuit being responsive to talking currents transmitted from said calling microphone over a circuit including said calling' microphone to connect said telephone repeater in circuit so that the said voice currents are amplified and retransmitted to the called telephone, and a circuit for inductirely receiving said talking" currents tor maintaining said relay operated independently of the circuit including said calling microphone.

et. A system ol the character described including a calling telephone and a called telephone, a two-Way trunk circuit for connecting said telephones, a pair oil Voice current relays, a telephone repeater includingl an agitating' member and an amplifying member for said circuit, relay mechanism associated with each o't said Voice current relays, means controlled by one ot said voice current relays and its associated relay mechanism for etliectively connecting the agitating member ot said repeater in series circ-uit with the calling telephone and the anmliliying member ot said repeater to the called telephone when voice currents are transmitted Jfrom the calling telephone, and means controlled by the other ot' said voice current relays and its associated relay mechanism for connecting the agitating member ot said repeater in series circuit with the called telephone and the amplifying member of said repeater to the calling` telephone when voice currents are transmitted from the called telephone.

` 5. l system ot the character described including' a calling telephone and a called telephone, a trunk circuit for connecting' said telephones, a pair of voice current relays and a repeater tor said trunk circuit, said repeater comprising an agitating member andan amplifying member, relay mechanism associated With each of said voice current relays, means controlled by one of' said yoice current relays when voice currents are transmitted from said calling telephone to operate said relay mechanism to elliectiyely connect the agitating member oit said telephone repcater in series circuit with the calling' telephone and the amplifying member et the repeater to the called telephone, said Lacasse voice current relay operating' to maintain the circuit in this condition as long' as vvoice currents are transmitted from the calling telephone, said other voice current relay beingl operative when voice current-s are transmitted from the called telephone to operate its associated relay mechanism to connect the agitating member of said repeater in series circuit with the called telephone and the amplifying member of said repeater to the calling telephone, said circuit remaining in this condition as long as Voice currents are transmitted from the called telephone.

6, telephone system ot the character described including` a calling telephone and a called telephone, a circuit for connecting' said telephones, a telephone repeater for said circuit, and mechanism including a chain of relays tor said circuit operative to connect said repeater in circuit so that when voice currents transmitted Ytrom the calling' telephone the repeater operates to amplify theyoice currents and retransmits them to the called telephone and when voice currents are transmitted Vfrom said called telephone the repeater is connected so that the voice currents are amplilied and retransmitted to the calling telephone, two relays in said chain or' relays controlling contacts in the voice current conductors of said circuit.

T. A telephone system oit the character described including` a calling telephone and a called telephone, telephone lines for said calling and called telephones, a circuit tor connecting said telephones, a repeater including` an agitating member and an amplitying member, and mechanism for said circuit controlled by the Voice currents transmitted from the calling and called telephones itor connecting the agitating member ot the repeater in series circuit with telephone lines of the calling' telephone and the amplifying member to the called telephone when the microphone oli' thev calling telephone is operated to transmit voice currents, and for connecting the agitating member ot' the repeater in series circuit with the telephone lincs ot the called telephone and the amplifying member of the repeater to the calling telephone When the microphone of the called telephone is operated to transmit voice currents.

8, A system of the character described including a calling telephone and a calledtelephone, a circuit 'tor connecting said telephones, a telephone repeater for said circuit normally disconnected from said calling telephone and said called telephone7 and yoicecurrent-controlled mechanism including a chain of relays for connecting said repeater so that when the subscriber at the calling telephone taillis, the voice currents Will be amplified by the repeater and transmitted to iso the called telephone and When the subscriber at the called telephone talks, theyvoice currents Will be amplified andtransmitted to the calling VVtelephone, two relays ot said chain of relays controlling` contacts in the voice current conductors of said circuit.

9. A telephone system of the character described including a Acalling and a called telephone, a circuit ior connecting said tele- 4 said voice current `relay for `connecting saidA agitating member in series circuit with the calling line and said amplifying member racross the called line.

l0. A telephone system or" the character described including a calling and a called telephone, a circuit Ator connectingsaid telephones, a voice` current relay adapted to beconnected across the calling telephones, av

telephone repeater having an agitating and an amplifying member, means controlled by said voice current relay for connecting said agitating member acrossL and in series circuit with the calling` line and said amplifying member across the called line, 'said means being also operative to remove the voice current relayl 'from across the calling telephone and for inductively connecting it to the callingr telephone.

1l. A. system of the character described including a calling telephone and a called telephone, a linlr circuit including a pair ot voice current relays for connecting said telephones, a repeater for said circuit having an agitatingand an amplifying member, means for bridging one of said voicecurrent relays across the calling telephone and the other of said relays across the called telephone, means controlled by one of said voice current relays when voice currents are transi'nitted from the calling telephone for removing both or said -voice current relays from across the calling and called telephone.J respectively,y and tor connectingthe agitatingmember of said repeater to the calling telephone and the amplitying member oi' said repeater to the called telephone.

l2. A system olA the character described including` a calling telephone and a called telephone, a link circuit including a pair oi' voice current relays for connecting said telephones, a repeater for said circuit having an agitatingr and an amplifying member, means for bridging one ot said voice current relays across the calling telephone andthe other o'tsaid relays across the called telephone, means controlled by one of said voice "current relays when voice currentsare transmitted from the calling telephone for removing bothlot said -voice current relays :from across the calling and called telephone, respectively, and for connecting the agitating member ot said repeater to the calling telephone and the amplifying member o'f` said repeater to the called telephone, and

`means, controlled by said other voice current relay when current is transmitted from the calledvtelephone for disconnecting the voice current relays from across the telephones and for connecting the agitating member of said repeater to the called telephone and the amplifying member of said repeater to the calling telephone.

13. A system of the character described including a calling telephone and a called telephone, a link circuit including a pair of voice current relays for connecting said telephones, a repeater tor said circuit having an agitating and an amplifying member, means for bridging one of said voice current relays across the calling telephone and the other ot said relays across the called teleplione, means controlled by one ot said voice current relays when voice currents are transmitted from the calling telephone for removing both of said voice current relaysA from across the `calling and called telephone, respectively, and for connecting the agitating member of said repeater to the calling telephone and the amplifying member of said repeater to the called telephone, and for inductively connecting said voice current relay to said calling telephone.

Signed by me at Chicago, in the county or Cook and State' of Illinois, this 14thV day of May, 1919. y

f SAMUEL SUEKOFF. 

